The invention relates to a process for the recovery by extraction of ethylene amines from a sodium chloride-containing solution, using a polar organic solvent which is immiscible with an aqueous salt solution, water-miscible and has a boiling point below 105.degree. C.
Such a process is known from the Japanese Patent Application published under no. 6523/'79. In this patent specification a process is described for extracting ethylene amines from an aqueous sodium chloride-containing solution using caustic soda and an organic solvent. According to the teaching of said patent specification the concentration of caustic soda in the solution must be at least 15% by weight for merely adequate extraction, but for favorable extraction a concentration in the range of 25-45% by weight is required. Mentioned as organic solvents are alcohols having 3 to 6 carbon atoms, dioxane, pyridine, and picolines. The resulting caustic soda solution is contaminated with a small amount of dissolved salt and solvent, rendering it unattractive for any other purpose. Another drawback is that the concentrated caustic soda solution is diluted significantly by its being added to the aqueous extraction mixture, so that it will be necessary to concentrate the sodium hydroxide solution by evaporation after its separation from the mixture in order to render it suitable for reuse in the extraction process. A further drawback is the precipitation of much sodium chloride from the extraction mixture as a result of the addition of caustic soda. This severely impurified precipitate consists primarily of very small salt particles which are difficult to purify and process.
From EP-A 0 110 470 it is known to extract ethylene amines using water-insoluble solvents. However, the separation by distillation of the obtained ethylene amines and solvent is very cumbersome if use is made of lower, water-immiscible alcohols as a result of a so-called maximum boiling point azeotrope being formed, and, more important, due to the boiling points of the alcohol and ethylene diamine being similar. The presently proposed invention provides a comparatively simple and economical technique for recovering ethylene amines from a salt-containing solution.